import java.util.Scanner;

public class Buy {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.println("请输入购买的钢管长度");
        int a = input.nextInt();
        int b = a / 3;
        if (a % 3 == 0) {
            System.out.println("购买的钢管根数为" + b);
        } else {
            System.out.println("购买的钢管根数为" + (b + 1));
        }

    }
}
